The CNS synthesizes and secretes several neuropeptides which attenuate the actions of morphine including CCK-8, Tyr-MIF, Phe-Leu-Phe-Gln-Pro- Gln-Arg-Phe-NH2 (NPFF), alpha-MSH and dynorphin(1-17). The anti-opioid model of tolerance and dependence poere obtained. Analyses